Method for machining grooves by a laser and honeycomb structure forming die and method for producing the same die

ABSTRACT

A laser groove machining method for forming bottomed grooves in a surface of a workpiece using a laser, wherein an emitting position of a laser beam which is to be emitted onto the workpiece is shifted relatively along groove forming positions at a high speed of 150 mm/min. or faster. Thus, melted portions which are melted by the laser beam can easily be separated, cooled and removed by shifting the laser beam emitting position at high speed. In addition, water may be jetted to the workpiece so as to form a pillar of water so that the laser beam is emitted through the interior of the pillar of water so formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a groove machining method for formingthin bottomed grooves in the surface of a metal workpiece using a laserand a honeycomb structure forming die using the same method and a methodfor producing the same die.

2. Description of the Related Art

Conventionally, machining using a laser has been used for welding andcutting a workpiece, but there has been no case where the lasermachining is used for machining grooves having bottoms or bottomedgrooves. In a cutting method using laser, a laser beam is emitted ontothe workpiece to melt it, and a melted portion is removed with an assistgas or high-pressure water. To be specific, a laser beam is emitted ontothe workpiece in such a manner as to be converged to a single locationthereon so as to form a through hole, and then the laser beam emittinglocation is shifted to form another through hole in the workpiece. Thus,the workpiece is cut by continuously forming through holes.

In a case where an attempt is made to use this method to form grooves,it is possible to form through grooves which have no bottoms, butbottomed grooves have not been formed using the method. In addition, inthe method in which the melted portion is removed by jettinghigh-pressure water, water remains on the surface of the workpiece,causing a problem that the path along which the laser beam is emitted isaltered owing to the water so remaining on the surface of the workpiece,whereby the laser beam cannot be emitted onto a desired position withaccuracy.

On the other hand, grid-like grooves are formed in a honeycomb structureforming die from which a ceramic honeycomb form is extruded. Most ofthese grooves are bottomed grooves which are large in depth and small inwidth. While grinding or electrical discharge machining has been used amethod for forming such grid-like grooves, as there is an increasingtendency that the widths of grooves are required to be narrower to suchas 100 μm or smaller, it is becoming more difficult to employ theaforesaid grinding and electrical discharge machining in which agrinding wheel and electrodes are physically used, respectively.

Incidentally, for example, a ceramic honeycomb structure made frommainly cordierite is produced by extruding the material using a formingdie. This honeycomb structure so formed is constituted by many cellswhich are formed by providing bulkheads in a grid-like fashion, and inmany cases the cells are each formed into, for example, a quadrilateralor hexagonal shape.

In addition, the aforesaid honeycomb structure forming die is used as ahoneycomb structure forming die having supply holes for supplying amaterial and grooves adapted to communicate with the supply holes,respectively, for forming the material supplied from the supply holesinto the aforesaid honeycomb shape.

In recent years, there has been a demand that the thickness of bulkheadsof the honeycomb structure is smaller and is, for example, 100 μm orsmaller. To cope with this demand, naturally, the width of the groovesof the honeycomb structure forming die must also be smaller.

However, if the width of the grooves of the honeycomb structure formingdie is made narrower, as required, the flowability of the material whichis supplied from the supply holes and then passes through the grooves isdeteriorated. This increases the forming pressure while forming iscarried out, leading to a risk that formability is reduced.

SUMMARY OF THE INVENTION

The invention was made in view of the problems inherent in the priorart, and an object thereof is to provide a method for forming narrow anddeep bottomed grooves using laser, and a honeycomb structure forming diefor forming a thin honeycomb structure without reducing the formabilityby making use of the bottomed grooves forming method and a method forproducing the same forming die.

According to an aspect of the invention, there is provided a lasergroove machining method for forming bottomed grooves in the surface of aworkpiece using laser, wherein an emitting position of laser which is tobe emitted on the workpiece is shifted relatively along groove formingpositions at a high speed of 150 mm/min. or faster.

According to this groove machining method of the invention, the relativeshifting speed of the laser beam emitting position is made to be theaforesaid high speed of 150 mm/min. or faster, whereby melted portionsresulting at the surface of the workpiece, through the emission of thelaser beam, can be blown off along the grooves so formed with an assistgas, thereby making it possible to separate, cool and remove the meltedportions. Namely, the melted portions can be separated, cooled andremoved with ease without forming through holes. This allows the lasermachining, which has conventionally been used only for cutting andwelding, to be applied to machining bottomed grooves.

According to another aspect of the invention, there is provided a methodfor producing a honeycomb structure forming die having supply holes forsupplying a material and grooves adapted to communicate with the supplyholes and formed into a grid-like configuration for forming the materialinto a honeycomb configuration, each groove having a groove depth whichis ten times or more as large as a groove width thereof, wherein inmachining the grooves in a die material, an emitting position of a laserbeam, which is to be emitted to a surface of the forming die materialwhich is opposite to a surface thereof where the grooves are formed, isshifted along groove forming positions.

According to this honeycomb structure forming die producing method ofthe invention, the method is adopted in which the laser beam is shiftedrelatively in machining the grooves, whereby grooves whose depth isgreater than the width can be produced with ease.

Namely, in a case where grooves are formed in the die material, only bya laser beam, melted portions formed through being subjected to theemission of the laser beam set as they are, making it difficult to formgrooves. Here, according to the method of the invention, as is describedabove, the laser beam is shifted relatively, whereby the melted portionscan be separated, cooled and removed with easy by separating, cooling toset, and removing the melted portions with an assist gas. Thus, narrowand deep grooves can be formed using a laser with ease.

According to a further aspect of the invention, there is provided ahoneycomb structure forming die having at least supply holes forsupplying a material and grooves adapted to communicate with the supplyholes and constructed to form the material into a honeycombconfiguration, wherein inclined portions are provided at corner portionsformed where bottom portions of the grooves intersect with sides of thesupply holes, and wherein, at the inclined portions, the depth of thegrooves gets deeper as the grooves approach the supply holes.

According to the honeycomb structure forming die of the invention, as isdescribed above, the depth of the grooves is not uniform but isconstructed to be deeper as the grooves approach the supply holes byproviding the inclined portions at the corner portions. Owing to this,the material is allowed to flow smoothly when it passes from the supplyholes to the grooves.

Namely, as the corner portions where the bottom portions of the groovesintersect with the sides of the supply holes are inclined, the material,which passes from the supply holes to the grooves, expands graduallyalong the inclined portions. Owing to this, when compared to a casewhere there is provided no inclined portion at the corner portions, thechange in flowing direction when the material expands in the widthdirection can be reduced. Because of this, the material is allowed toflow smoothly when it penetrates into the grooves from the supply holes.

Then, owing to this, even in case the width of the grooves is madenarrower, an increase in forming pressure can be suppressed, therebymaking it possible to maintain a superior formability.

According to another aspect of the invention, there is provided a methodfor producing a honeycomb structure forming die having at least supplyholes for supplying a material and grooves adapted to communicate withthe supply holes and constructed to form the material into a honeycombconfiguration, comprising the steps of forming the supply holes from ahole forming surface of a die material, thereafter jetting water togroove forming positions on a groove forming surface opposite to thehole forming surface so as to form a pillar of water so that a laserbeam is emitted through the interior of the pillar of water andimplementing scanning of the emitted laser beam in which the laser beamemitting position is shifted along the groove forming positions in sucha manner as to pass along the same groove forming positions a pluralityof times, increasing the number of times of scanning the emitted laserbeam in the vicinity of corner portions formed where bottom portions ofthe grooves intersect with sides of the supply holes and forminginclined portions at the corner portions so that the depth of thegrooves gets deeper as the grooves approach the supply holes.

According to this aspect of the invention, as described above, the laserbeam which is caused to pass through the pillar of water is used tomachine the grooves. In addition, the depth of the grooves is made toget deeper gradually by implementing the emission scanning of the laserbeam as described above.

Thus, the depth of the grooves can be changed locally by changing thenumber of times of implementation of the emission scanning locally byadopting the laser machining method that has just been described above.

Owing to this, according to the aspect of the invention, the number ofimplementations of the emission scanning is increased in the vicinity ofthe corner portions formed where the bottom portions of the groovesintersect with the sides of the supply holes by changing the number ofimplementation of the emission scanning, whereby the inclined portionsare formed at the corner portions so that the depths of the groovesbecome deeper as the grooves approach the supply holes.

In addition, according to the aspect of the invention, the laser beam isemitted through the pillar of water as described above, whereby thelaser beam advances while being confined within the diameter of thepillar of water, so that the width of the grooves can be controlled tofall within the diameter of the pillar of water with accuracy. Owing tothis, the groove machining that can well meet the accuracy required forthe honeycomb structure forming die can be implemented with ease.

Thus, according to an aspect of the invention, the aggressive adoptionof the aforesaid laser machining method enables the realization of thelocal change in depth of the grooves, which has been extremely difficultto be realized by the conventional grinding or electrical dischargemachining. In addition, in particular, the honeycomb structure formingdie which can provide the smooth flow of the material can be obtained bychanging the depth of the grooves in such a manner as to form theinclined portions at the corner portions.

The present invention may be more fully understood from the descriptionof preferred embodiments of the invention set forth below, together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an explanatory view showing the construction of a lasermachining apparatus according to a first embodiment of the invention;

FIG. 2 is an explanatory view showing the construction of a lasermachining apparatus according to a second embodiment of the invention;

FIG. 3A is a plan view of a honeycomb structure forming die according toa third embodiment of the invention,

FIG. 3B is an enlarged view of a main part thereof and

FIG. 3C is a sectional view taken along the line III—III in FIG. 3B;

FIG. 4A is a plan view of a honeycomb structure forming die according toa fourth embodiment of the invention, and

FIG. 4B is an enlarged view of a main part thereof;

FIG. 5 is a graph showing a relationship between the shift speed of alaser beam emitting position and the depth and width of a bottomedgroove to be formed according to a sixth embodiment of the invention;

FIG. 6A is a plan view of a honeycomb structure forming die according toa seventh embodiment of the invention,

FIG. 6B is an enlarged view of a main part thereof and

FIG. 6C is a sectional view taken along the line VI—VI in FIG. 6B;

FIG. 7 is a sectional view of a honeycomb structure forming die taken asa comparison example which is produced using a conventional electricaldischarge machining;

FIG. 8A is a plan view of a honeycomb structure forming die according toan eighth embodiment of the invention, and

FIG. 8B is an enlarged view of a main part thereof;

FIG. 9 is an enlarged explanatory view of an inclined portion of ahoneycomb structure forming die according to a ninth embodiment of theinvention; and

FIG. 10 is an enlarged explanatory view of an inclined portion of ahoneycomb structure forming die taken as a comparison example which isproduced using a conventional cutting process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

Referring to FIG. 1, a laser groove machining method according to anembodiment of the invention will be described below.

In this embodiment, a bottomed groove 70 is formed in a surface of aworkpiece 7 using laser. As this occurs, an emitting position of a laserbeam 1 which is to be emitted to the workpiece 7 is shifted relativelyalong groove forming positions at a high speed of 150 mm/min. or faster.

This will be described in detail below.

A laser machining apparatus 2 shown in FIG. 1 is used in thisembodiment. The laser machining apparatus 2 has a laser generatingportion 21 for generating a laser beam 1, a laser head 22 for stoppingthe laser beam so generated to a desired diameter, an optical fiberportion 23 for providing a connection between the laser generatingportion 21 and the laser head 22 so as to guide the laser beam 1 and anassist gas supply portion 25 for supplying to the laser head 22 anassist gas which is to be jetted around the laser beam 1. In addition,the apparatus has a bed 26 designed not only to hold the workpiece 7thereon but also to be shifted on a plane. A bed driving portion isincorporated in the bed, and a control panel 29 is connected to the beddriving portion, the assist gas supply portion 25 and the lasergenerating portion 21 to control them.

As shown in the figure, the workpiece 7 is a metallic plate which is 15mm thick, 200 mm wide and 200 mm long. The metallic plate is made of JIS(Japanese Industrial Standard) SKD 61 (ASTM H13). Of course, theworkpiece may be made of different materials in different sizes.

In this embodiment, a 0.1 mm wide and 2.0 mm deep bottomed groove willbe formed in the workpiece 7.

To be specific, the workpiece 7 is held on a support device, not shown,in such a manner as to move horizontally. Then, a laser beam 1 and anassist gas 15 are jetted from the laser machining apparatus 2 while theworkpiece 7 is being shifted in a direction indicated by an arrow Ashown in FIG. 1. The shifting speed of the workpiece 7 used in thisembodiment was 240 mm/min. which is faster than 150 mm/min. Note thatwhile the laser machining apparatus 2 may be used for conventionalcutting, the maximum shifting speed of workpiece for such an applicationis 100 mm/min. In this embodiment, the emitting position of the laserbeam 1 was shifted relatively at the speed which largely exceeds themaximum speed.

Accordingly, portions of the workpiece to which the laser beam 1 isemitted are sequentially melted, and thereafter the melted portions areseparated, cooled and removed. As a result, an extremely shallowbottomed groove 70 is formed by a single emission of the laser beam 1.Then, in this embodiment, the emitting position of the laser beam 1 wasshifted repeatedly in such a manner as to pass along the groove formingpositions 150 times, whereby as has been described above, the narrow anddeep bottomed groove 70 was obtained, with accuracy, which is 0.1 mmwide and 2.0 mm deep.

(Second Embodiment)

In this embodiment, a laser machining apparatus 3 which can, as shown inFIG. 2, jet a pillar of water was used in lieu of the laser machiningapparatus 2 used in the first embodiment. As shown in FIG. 2, the lasermachining apparatus 3 has a laser generating portion 31 for generating alaser beam, a laser head 32 for changing the laser beam so generated toa desired diameter, an optical fiber portion 33 for providing aconnection between the laser generating portion 31 and the laser head 32so as to guide the laser beam, a high-pressure water supply portion 35for supplying, to the laser head portion 32, high-pressure water for usein jetting a pillar of water 18 around the laser beam 1 and a nozzle 36for jetting high-pressure water in the form of a pillar of water 18. Inaddition, as in the case of the first embodiment, the apparatus has thebed 26 designed not only to hold the workpiece 7 thereon but also to beshifted on a plane. The bed driving portion, the high-pressure watersupply portion 35 and the laser generating portion 31 are incorporatedin the bed and are connected to a control panel 39 for controlling them.

Then, water was jetted to the workpiece 7 using the laser machiningapparatus 3 to form a pillar of water 18 and the laser beam 1 wasemitted to the workpiece 7 through the pillar of water 18. In addition,the emitting position of the laser beam 1 was shifted relatively at thehigh speed of 240 mm/min. as with the first embodiment. The laser beam 1was emitted 150 times as with the first embodiment.

In this embodiment, the laser beam 1 is emitted to the workpiece 7 whilebeing confined within the pillar of water 18, and melted portions whichare melted by the laser beam 1 are efficiently separated, cooled andremoved with water jetted therearound, whereby a bottomed groove can bemachined more accurately. As a result, in this embodiment, too, a narrowand deep bottomed groove 70 was obtained, with accuracy, which is 0.1 mmwide and 2.0 mm deep.

In addition, in the first and second embodiments, it is desirable thatthe emitting position of the laser beam is shifted repeatedly in such amanner as to pass over the groove forming positions a plurality oftimes. In this case, the amount of machining through a single emissionof the laser beam can be set to a limited amount, and hence the amountof melting through the single emission of the laser beam becomes small.Owing to this, melted portions can be blown off with, for example, theassist gas along the groove being formed, whereby the melted portionscan easily be separated, cooled and removed. Consequently, a bottomedgroove can be machined with higher accuracy.

In addition, the workpiece may be made of another metallic material.While the groove machining method using the laser beam may also beapplied to a workpiece which is made of ceramics or any other material,the method can be effective particularly when it is applied to theworkpiece made of a metallic material. Namely, in a case where theworkpiece is made of a metallic material, melted portions which aremelted through emission of a laser beam tend to set as they are at theiroriginal positions, this making groove machining in the metallicmaterial difficult. However, as is described above, relatively shiftingthe laser beam emitting position at the high speed of 150 mm/min. orfaster can provide the aforesaid function and effect and enable groovesto be machined in metallic materials.

In addition, the bottomed groove may be a bottomed groove having a depthwhich is ten times or more greater than the width thereof. In this case,in particular, the aforesaid superior function and effect caneffectively be used. Namely, according to the invention, the emittingposition of the laser beam which is emitted to the workpiece is shiftedrelatively along the groove forming positions at the high speed of 150mm/min. or faster. Owing to this, the melted portions which are meltedthrough emission of the laser beam can easily be separated, cooled andremoved by blowing off the melted portions, with, for example, theassist gas, along the groove being formed. Consequently, the bottomedgroove which is greater in depth than in width can be machined withhigher accuracy. Thus, according to the invention, a bottomed groove canbe formed which has a depth which is ten times or more greater than thewidth thereof.

Note that according to the invention, even a bottomed groove can beformed which has a depth which is twenty times or more greater than thewidth thereof.

Additionally, the bottomed groove may be a U-shaped groove. Here, theU-shaped groove can be defined as a groove in which, assuming that acircle R contacts both side walls of a sectional curve of the groove andthe bottom thereof, respectively, the sectional curve connecting theside walls of the groove with the bottom thereof always passes outsideof the circle R.

In this case, too, the aforesaid superior function and effect of theinvention can be used effectively.

(Third Embodiment)

In this embodiment, a honeycomb structure forming die is produced usingthe laser groove machining method according to the second embodiment ofthe invention.

As shown in FIGS. 3A to 3C, a honeycomb structure forming die 8 which isto be produced in this embodiment has supply holes 81 for supplying amaterial and grooves 82 adapted to communicate with the supply holes 81and constructed into a grid-like configuration for forming the materialinto a honeycomb configuration, and each groove 82 has a depth which isten times or more greater than the width thereof.

In addition, the grooves 82 according to this embodiment are formed intoa square grid configuration relative to a grooves forming portion 820which protrudes from a surrounding area.

In producing a honeycomb structure forming die 8 configured as describedabove, firstly, a die material is prepared which has a grooves formingportion 820 which protrudes as described above. Then, the supply holes81 (FIG. 3C) are formed, using a drill, from the back of the diematerial or an opposite side to a side where the grooves forming portion820 is provided. Next, grooves 82 are formed in the grooves formingportion 820 using the same method as that described in the secondembodiment.

Namely, the die material 80 was set on the bed 26 of the laser machiningapparatus 3 shown in FIG. 2 and the emitting position of the laser beam1 was shifted repeatedly vertically and horizontally in a grid-likefashion. The relative shifting speed and the number of times of repeatedshifting of the emitting position at that time were 240 mm/min. and 150times, respectively, which are identical to those described in thesecond embodiment.

Accordingly, a honeycomb structure forming die 8 could be obtained withaccuracy which has slit grooves 82 each being 0.1 mm wide and 2.0 mmdeep.

(Fourth Embodiment)

As shown in FIGS. 4A, 4B, this embodiment provides an example in whichthe grid configuration of the grooves 82 of the honeycomb structureforming die 8 described in the third embodiment is modified to ahexagonal shape.

In this embodiment, similar conditions to those in the third embodimentwere used to produce a honeycomb structure forming die except that theshifting route of the emitting position of the laser beam 1 was changed.In this case, in particular, grooves 82 in hexagonal configuration,which could not be formed only with the electrical discharge machining,can be formed efficiently and accurately using the grooves machiningmethod employing laser, and the grooves forming process can largely berationalized, whereby the cost and time required to produce honeycombstructure forming dies can be reduced.

(Fifth Embodiment)

This embodiment provides an example in which the grooves of thehoneycomb structure forming die according to the third embodiment isformed under the following laser machining conditions. In thisembodiment, the grooves 82 were formed with the laser machiningapparatus 3 described in the third embodiment under laser machiningconditions in which the frequency is 400 Hz, pulse is 120 μm/sec,voltage is 700V, hydraulic pressure is 100 bar, STEP is 10 μm, shiftingspeed is 240 mm/min. and the number of times of scanning is 80 to 130times.

As a result, 40 to 150 μm wide and 2.0 to 3.5 mm deep grooves 82 wereformed in the honeycomb structure forming die 8.

(Sixth Embodiment)

In this embodiment, experiments were made to obtain a relationshipbetween the shifting speed of the emitting position of the laser beam 1and the depth and width of the bottomed grooves 70 using the lasermachining apparatus 3 according to the second embodiment. Note that thelaser machining conditions were identical to those in the fifthembodiment except for the shifting speed of the emitting position of thelaser beam 1.

The results of the experiments are shown in FIG. 5. In the figure, theaxis of abscissas represents the shifting speed of the emitting positionof the laser beam 1 whereas the axis of ordinates represents the depthand width of the bottomed grooves 70.

In addition, as is seen from the figure, setting the shifting speed ofthe emitting position of the laser beam 1 to 150 mm/min. or faster canprovide an advantage that the machining time per scan can be reduced. Inaddition, with the number of times of scanning being the same, there isprovided an advantage that the bottomed grooves 70 can be formed deeper.

As a result, it is found that in forming the bottomed grooves 70 byemitting the laser beam 1, the efficiency can considerably be improvedby setting the shifting speed of the emitting position of the laser beam1 to 150 mm/min. or faster.

Thus, in producing honeycomb structure forming dies by the laser beam,it is preferable to relatively shift the emitting position of the laserbeam at the shifting speed of 150 mm/min. or faster. As this occurs,melted portions formed by being subjected to emission of the laser beamcan easily be separated, cooled and removed by separating, cooling toset and removing the melted portions so formed, along a groove beingformed, with, for example, an assist gas. Consequently, as has beendescribed above, grooves whose depth is greater than the width can beformed with higher accuracy.

In addition, it is preferable to form a pillar of water by jetting waterto the die forming material so that the laser beam is emitted to the dieforming material while being caused to pass through the pillar of water.As this occurs, the laser beam is emitted to the die forming materialwhile being confined within the pillar of water, and melted portions bythe laser beam so emitted are efficiently separated, cooled and removedby water jetted around the melted portions, whereby the grooves can bemachined with higher accuracy.

In addition, it is preferable that the emitting position of the laserbeam is repeatedly performed in such a manner as to pass along thegrooves forming positions a plurality of times. As this occurs, themachining amount per single emission of laser beam can be set small andtherefore the amount of melting through the emission of laser beambecomes small, whereby the melted portion can easily be separated,cooled and removed by for example, blowing off the melted portion alongthe groove being formed with the assist gas. Thus, as has been describedabove, the grooves whose depth is greater than the width can be formedwith higher accuracy.

Furthermore, the grooves can be formed into a grid-like configuration inwhich circular, triangular, square or hexagonal shapes are continuouslyconnected to each other. With any of the shapes, the aforesaid superiorfunction and effect can effectively be used. Thus, the grooves formingprocess can considerably be rationalized by putting the groove machiningby the laser beam to practical use while avoiding high-cost electricaldischarge machining.

Moreover, it is preferable that the material of the honeycomb structureforming die is cemented carbide or alloy tool steel. While the groovemachining method using the laser beam can be applied to a workpiece madeof ceramics or any other material, the method becomes effective whenapplied, in particular, to a workpiece made of the aforesaid cementedcarbide or alloy tool steel (for example, JIS, SKD61) or any other steelmaterial. Namely, in a case where a workpiece is made of the aforesaidmaterial, melted portions which are partially melted through emission ofa laser beam tend to set as they are at their original positions, thismaking the groove machining by the laser beam difficult. However, theaforesaid superior function and effect can be obtained by relativelyshifting the laser emitting position as is described above, wherebygrooves can be machined in the metallic material.

In addition, when used herein, the cemented carbide material means apowder metallurgy alloy which is produced by hardening tungsten carbidepowder containing cobalt powder as a binder with a press and thereaftersintering the powder so hardened.

Furthermore, it is preferable that the width of the grooves is 40 to 150μm and that the depth thereof is 2.0 to 3.5 mm. The aforesaid superiorfunction and effect can effectively employed in particular in formingthose narrow and deep grooves.

Moreover, the tolerance of the depth of the slit grooves can be limitedto 0.3 mm or less. In this case, in particular, the aforesaid superiorfunction and effect can effectively be employed. Namely, according tothe method of the invention, the laser beam can be shifted relatively inmachining the grooves, whereby the melted portions can be separated,cooled and removed by separating, cooling to set and removing the meltedportion along the groove being formed with the assist gas. Consequently,the bottomed grooves having the depth tolerance of 0.3 mm or less can beformed by optimizing the shifting speed.

(Seventh Embodiment)

Referring to FIGS. 2 and 6A to 6C, a seventh embodiment according to theinvention will be described below.

A honeycomb structure forming die 8 according to this embodiment is, asshown in FIGS. 6A to 6C, a honeycomb structure forming die 8 having atleast supply holes 81 for supplying a material and grooves 82 adapted tocommunicate with the supply holes 81 and constructed to form thematerial into a honeycomb configuration. In the honeycomb structureforming die 8 according to the embodiment, inclined portions 85 areformed at corner portions formed where bottom portions 830 of thegrooves 82 intersect with sides 810 of the supply holes 81, and thedepth of the grooves 82 is made to be deeper gradually as the bottomportions approach the supply holes 81 at the inclined portions 85.

The laser machining apparatus 3 shown in FIG. 2 is used to produce thehoneycomb structure forming die 8.

As shown in the figures, a die material 7, which is a workpiece to bemachined, is a square metallic plate which is 15 mm thick, 200 mm wideand 200 mm long and is formed of JIS, SKD61. Of course, die materials insizes and of materials which are different from those described abovemay be used.

In this embodiment, 0.1 mm wide and 2.0 mm deep slit grooves are formedin the die material 7. In addition, in this embodiment, as shown in FIG.6C, the supply holes 81 had been provided in advance, by drilling,before the grooves 82 were machined.

Then, the die material 7 is held on a support device, not shown, in sucha manner as to move in horizontal directions. Then, while shifting thedie material 7 in a direction indicated by an arrow A illustrated inFIG. 2, water is jetted from the laser machining apparatus 8 to a grooveforming position on a groove forming surface of the die material 7 so asto form a pillar of water 18 and a laser beam 1 is emitted through thepillar of water 18. Furthermore, the emitting position of the laser beam1 is shifted along groove forming positions and emission scanning isperformed in which the emitting position of the laser beam is caused topass along the groove forming positions a plurality of times.

As this occurs, the shifting speed of the die material 7 was set to 240mm/min., which is faster than 150 mm/min. Then, firstly, the emissionscanning was performed in such a manner that the laser emitting positionwas caused to pass through the entire groove forming positions 150 timesevenly, whereby as has been described above, narrow and deep grooves 82(70) were obtained which are 0.1 mm wide and 2.0 mm deep.

Moreover, in this embodiment, the number of times of emitting the laserbeam was designed to be increased in such a manner that the number oftimes of scanning increases as the bottom portions of the grooves 82approach the supply holes 81 in the vicinity of the corner portionsformed where the bottom portions 830 of the grooves 82 so formedintersect with the side 810 of the supply holes 81, whereby, as shown inFIG. 6c, the grooves 82 were machined in such a manner that the depth ofthe grooves 82 become gradually deeper as the bottom portions of thegrooves 82 approach the supply holes 81 and inclined portions 85 areprovided at the corner portions.

Next, the function and effect of this embodiment will be describedbelow.

As has been described above, in the honeycomb structure forming die 8according to this embodiment, the depth of the grooves 82 is notuniform, and the corner portions are inclined to form the inclinedportions 85 so that the depth of the grooves 82 becomes deeper as thebottom portions of the grooves 82 approach the supply holes 81. Owing tothis construction, the material passing from the supply holes 81 to thegrooves 82 is allowed to flow smoothly.

Namely, as the corner portions where the bottom portions 830 of thegrooves 82 intersect with the sides 810 of the supply holes 81 areinclined, the material passing from the supply holes 81 to the groovesexpands gradually along the inclined portions 85. Owing to this, whencompared to a case where no inclined portion 85 is provided at thecorner portions, the variation in the flowing direction occurring whenthe material expands in the widthwise direction can be made small,whereby the material is allowed to flow smoothly when it penetrates fromthe supply holes 81 into the grooves 82. Then, because of this, even ina case where the width of the grooves 82 is as small as 0.1 mm, asdescribed above, an increase in forming pressure can be suppressed,whereby superior formability can be maintained.

In addition, the unique machining method that has been described aboveis adopted in machining the superior grooves 82 of the honeycombstructure forming die 8. Namely, the laser beam 1 is used which iscaused to pass through the pillar of water 18, and the number of timesof emission scanning is changed locally, whereby the depth of thegrooves can be changed locally.

In this embodiment, the number of times of emission scanning isincreased in the vicinity of the corner portions, whereby the inclinedportions 85 can be formed with ease, thereby making it possible toobtain a configuration in which the depth of the grooves 82 is madedeeper as the bottom portions of the grooves 82 approach the supplyholes 81.

Thus, it is difficult to obtain these advantages with the conventionallyused grinding or electrical discharge machining method.

COMPARISON EXAMPLE

A comparison example provides an example in which the grooves 82machining method is changed to the conventional electrical dischargemachining and a honeycomb structure forming die 9 is obtained in whichthe depth of grooves 82 is made uniform. The other portions of theconstruction of the die remains the same as that of the honeycombstructure forming die in the seventh embodiment.

Shown in FIGS. 6C and 7 are flowing directions of the material whichtake place when honeycomb structures are extrusion formed using thehoneycomb structure forming die 8 of the seventh embodiment and thehoneycomb structure forming die 9 of the comparison example,respectively. Note that, for example, a ceramic material produced bymixing a plurality of kinds of powder, which can be raw materials ofcordierite, with a binder can be used as the ceramic material for thehoneycomb structures. In addition, material powder whose grain size is60 μm or smaller can be adopted.

As shown in FIG. 7, in the case of the conventional honeycomb structureforming die 9, as the grooves 82 are formed in such a manner that thedepth thereof becomes uniform, the flow of the forming material which issupplied into the supply holes 81 in a direction indicated by an arrow Bis changed to directions indicated by arrows D which are normal to thedirection indicated by the arrow B at the corner portions where thematerial so supplied intersects with the grooves 82 and then is changedto a direction indicated by an arrow E, as a result of collision betweenthe material so supplied, so as to be extruded from the slit grooves 82for extrusion forming a honeycomb structure.

On the other hand, as shown in FIG. 6C, in the case of the honeycombstructure forming die 8 according to the invention, as the inclinedportions 85 are provided and the depth of the grooves 82 is constructedto get deeper gradually as the bottom portions of the grooves 82approach the supply holes 81, the flow of the material supplied into thesupply holes 81 in a direction indicated by an arrow B is changed todirections indicated by arrows C along the inclination of the inclinedportions 85 at the corner portions where the material so suppliedintersects with the grooves 82. Then, the flow of the material isfinally changed to a direction indicated by an arrow E so as to beextruded from the grooves 82 for extrusion forming a honeycombstructure.

Thus, since the variation in flowing direction of the material issmaller when the honeycomb structure forming die according to theseventh embodiment is used than when the honeycomb structure forming dieof the comparison example, the increase in forming pressure can besuppressed, thereby making it possible to maintain superior formabilityeven when the width of the slit grooves becomes narrower.

(Eighth Embodiment)

As shown in FIGS. 8A, 8B, this embodiment provides an example in which ahoneycomb structure is produced which has a honeycomb structure havingslit grooves 82 formed into a hexagonal grid-configuration.

In this case, the scanning path of the emitted laser beam 1 employed inthe seventh embodiment is devised such that the trace of the emittedlaser beam 1 so scanned is formed into the hexagonal grid-likeconfiguration.

In this case, too, a similar function and an effect, to those providedin the seventh embodiment, can be obtained.

(Ninth Embodiment)

In this embodiment, similarly to the seventh embodiment, inclinedportions 85 are provided in a honeycomb structure forming die 8, and theconfiguration thereof is measured in a quantitative fashion.

As shown in FIG. 9, in the honeycomb structure forming die 8 accordingto this embodiment, the diameter of supply holes 81 is 1 mm, and thepitch of the supply holes is 2 mm. In addition, the inclined portions 85are provided in a similar manner to that used in the seventh embodiment.Note that the width of grooves 82 formed is 0.1 mm, which is similar tothat of the grooves 82 formed in the seventh embodiment.

As shown in the figure, the inclined portion 85 according to theembodiment is formed over a distance L ranging from 0.3 mm and more fromthe side 810 of the supply hole 81, and the final depth D thereof is 0.3mm and above.

In this embodiment, as shown in FIG. 10, for the purpose of comparison,the method for forming grooves 82 was changed to the grinding method anda honeycomb structure forming die 9 having no inclined portions wasproduced. Then, an extrusion forming was actually performed using thehoneycomb structure forming die 9 (a comparison article) which is acomparison example with the honeycomb structure forming die 8 accordingto the embodiment (an article according to the invention) to make acomparison between forms so produced using the respective dies.

The results of the comparison disclosed that when compared with thecomparison article, with the article according to the invention, thematerial flowed smoothly and superior extrusion formability could beobtained.

It was found from the results of the comparison that, in the event thatthe width of the grooves 82 is 0.1 mm as is described above, theflowability of the material which passes from the supply holes 81 to thegrooves 82 can be improved by providing the inclined portions 85 whichare formed over the distance L ranging from 0.3 mm and above from thesides 810 of the supply holes 81 and whose final depth D thereof is 0.3mm and above.

In addition, as a result, in a case where the flowability of thematerial may remain the same as that provided by the conventionalexample, the required flowability can be secured sufficiently even ifthe depth of the grooves 82 is made shallow. Owing to this, since thedepth of the grooves 82 can be made shallower by, for example, in theorder of one third of the final depth D, the machining efficiency can beimproved.

In the above embodiment, the inclined portions at the corner portionsmay take the form of a fine inclination which would result when thecorner portions were chamfered or a relatively long taper. Furthermore,the inclined portions may be straight or curved.

In addition, the slit grooves can be laid out in a square or a hexagonalgrid-like configuration.

Furthermore, a narrow width of, for example, 40 to 150 μm may be adoptedas the width of the grooves. In this case, too, a smooth flow of theforming material, such as described above, can be secured. In addition,the depth of the grooves may be set to be ten times or more as large asthe width thereof. In this case, too, the inclination of the cornerportions functions effectively, and the deterioration in flowability ofthe forming material can be suppressed.

Moreover, it is preferable that the laser beam emitting position isshifted at the relative speed of 150 mm/min. or faster, whereby groovemachining can be progressed step by step while melted portions, whichhave been melted through emission of the laser beam, are separated andremoved with ease. In contrast, in the event that the relative shiftingspeed is below 150 mm/min., the separation and removal of the meltedportions cannot be implemented sufficiently, thereby causing a problemthat the groove forming efficiency is deteriorated.

In addition, it is preferable that the inclined portions are providedwithin a distance ranging up to 0.5 mm from the sides of the supplyholes. In this case, the inclined portions can be formed relativelyeasily.

Additionally, it is preferable that the inclined portions are providedover a distance ranging from 0.3 mm and above from the sides of thesupply holes and that the final depth of the inclined portions is 0.3 mmand above.

In this case, the advantage of a smooth flow of the material can beexhibited sufficiently which results from the existence of the inclinedportions.

While the invention has been described by reference to the specificembodiments chosen for purposes of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

What is claimed is:
 1. A method for producing a honeycomb structureforming die having supply holes for supplying a material and groovesadapted to communicate with said supply holes and formed into agrid-like configuration for forming said material into a honeycombconfiguration, each groove having a groove depth which is ten times ormore as large as a groove width thereof, wherein, in machining saidgrooves in a die material, an emitting position of a laser beam which isto be emitted to a surface of said die material which is opposite to asurface thereof where said supply holes are formed, is shifted alonggroove forming positions.
 2. A method for producing a honeycombstructure forming die as set forth in claim 1, wherein, when shiftingsaid emitting position of said laser beam along said groove formingpositions, said emitting position of said laser beam is shiftedrelatively along said groove forming positions at a high speed of 150mm/min. or faster.
 3. A method for producing a honeycomb structureforming die as set forth in claim 1, wherein water is jetted to said diematerial so as to form a pillar of water, and wherein said laser beam isemitted onto said die material through the interior of said pillar ofwater.
 4. A method for producing a honeycomb structure forming die asset forth in claim 1, wherein shifting of said emitting position of saidlaser beam is repeatedly performed in such a manner as to pass over saidgroove forming positions a plurality of times.
 5. A method for producinga honeycomb structure forming die as set forth in claim 1, wherein saidgrooves are formed into a grid-like configuration comprising round,triangular, square of hexagonal shapes which are continuously connectedto each other.
 6. A method for producing a honeycomb structure formingdie as set forth in claim 1, wherein the material of said honeycombstructure forming die is a cemented carbide or alloy tool steel.
 7. Amethod for producing a honeycomb structure forming die as set forth inclaim 1, wherein the width of said slit grooves is 40 to 150 μm and thedepth thereof is 2.0 to 3.5 mm.
 8. A method for producing a honeycombstructure forming die as set forth in claim 1, wherein the tolerance inthe depth of said grooves is 0.3 mm or less.
 9. A method for producing ahoneycomb structure forming die having at least supply holes forsupplying a material and grooves adapted to communicate with said supplyholes and constructed to form said material into a honeycombconfiguration, comprising the steps of forming said supply boles from ahole forming surface of a die material, thereafter jetting water togroove forming positions on a groove forming surface opposite to saidhole forming surface so as to form a pillar of water so that a laserbeam is emitted through the interior of said pillar of water andimplementing scanning of said emitted laser beam in which said laserbeam emitting position is shifted along said groove forming positions insuch a manner as to pass along said same groove forming positions aplurality of times, increasing the number of times of scanning saidemitted laser beam in the vicinity of corner portions formed wherebottom portions of said grooves intersect with sides of said supplyholes so that the depth of said grooves gets deeper as said groovesapproach said supply holes and forming inclined portions at the cornerportions.
 10. A method for producing a honeycomb structure forming dieas set forth in claim 9, wherein shifting of said laser beam emittingposition is performed at a relative speed of 150 mm/min. or faster. 11.A method for producing a honeycomb structure forming die as set forth inclaim 9, wherein said inclined portions are formed within a distanceranging up to 0.5 mm from the sides of said supply holes.
 12. A methodfor producing a honeycomb structure forming die as set forth in claim 9,wherein said inclined portions are formed over a distance ranging from0.3 mm and above from the sides of said supply holes and wherein thefinal depth of said inclined portions is 0.3 mm and above.